C/1998 P1 Williams
more info
Comet C/1998 P1 was discovered on 10 August 1998 by Peter Williams (Heathcote, Australia). At the moment of discovery, C/1998 P1 was about 2 months before its perihelion passage and it was last observed in the mid-May 1999.
Comet had its closest approach to the Earth on 28 July 1998 (0.887 au), about 2 weeks before its discovery.
This is a comet with nongravitational effects strongly manifested in positional data fitting.
Solutions given here are based on data spanning over 0.758 yr in a range of heliocentric distances: 1.56 au – 1.15 au (perihelion) – 3.13 au.
This comet suffers large planetary perturbations during its passage through the planetary system; these perturbations lead to a significantly more tight future orbit with semimajor axis of about 830 au. See also Królikowska 2020.

solution description
number of observations 461
data interval 1998 08 11 – 1999 05 15
data type perihelion within the observation arc (FULL)
data arc selection entire data set (STD)
range of heliocentric distances 1.56 au – 1.15 au (perihelion) – 3.13 au
type of model of motion NS - non-gravitational orbits for standard g(r)
data weighting YES
number of residuals 905
RMS [arcseconds] 0.78
orbit quality class 1b
orbital elements (barycentric ecliptic J2000)
Epoch 1697 06 13
perihelion date 1998 10 15.93555275 ± 0.00021704
perihelion distance [au] 1.13365411 ± 0.00000574
eccentricity 0.99971266 ± 0.00000870
argument of perihelion [°] 294.701977 ± 0.000347
ascending node [°] 156.288093 ± 0.000153
inclination [°] 145.810017 ± 0.000056
reciprocal semi-major axis [10-6 au-1] 253.46 ± 7.67
file containing 5001 VCs swarm
1998p1n1.bmi
Upper panel: Time distribution of positional observations with corresponding heliocentric (red curve) and geocentric (green curve) distance at which they were taken. The horizontal dotted line shows the perihelion distance for a given comet whereas vertical dotted line — the moment of perihelion passage.
Lower panel (panels): O-C diagram for this(two) solution (solutions) given in this database, where residuals in right ascension are shown using magenta dots and in declination by blue open circles.
Six 2D-projections of the 6D space of original swarm including 5001 VCs. Each density map is given in logarithmic scale presented on the right in the individual panel.